Reverend deluding himself

May 7, 2008

Updated: Tuesday, June 8, 2010 (09:03)

THE Reverend Philip Foster is deluding himself, which he is entitled to do (Letters, April 30). He is after all a man of God. I will expose his delusion with some simple physics that everyone who bothered to listen to their physics or chemistry teacher sh

THE Reverend Philip Foster is deluding himself, which he is entitled to do (Letters, April 30). He is after all a man of God.

I will expose his delusion with some simple physics that everyone who bothered to listen to their physics or chemistry teacher should know.

First, let's get the scientific terms correct in the reader's mind: temperature is a measure of how hot things are at the point of time and place where you are taking the measurement. Temperature is not a measure of the amount of energy stored in the environment, or more correctly, the system you are measuring.

Heat is an expression of the amount of thermal energy stored in a system. It is measured in a variety of different ways but for convenience I will use calories since everyone has an idea of calories, such as the amount of energy contained in a chocolate bar. You do not measure the amount of energy in a chocolate bar with a thermometer.

So why is the Rev Foster wrong in saying that, because the temperature of the earth hasn't risen significantly in the last 10 years in spite of rising CO2 levels, global warming is a myth? The answer lies in latent heat of melting and latent heat of evaporation.

A calorie is the amount of energy needed to raise the temperature of 1cc of water 1 degree C. It takes 80 calories to turn 1cc of water from ice to water at 0 deg C. The temperature does not rise as those 80 calories are absorbed by the ice: the ice melts instead. Once the ice has melted, it takes only another 100 calories for the 1cc of water to reach boiling point. At this point the temperature ceases to rise as the energy is absorbed by the process of evaporation. For 1cc of water at 100 degrees C. to evaporate takes a further 539 calories - which is why steam scalds so easily, it contains a lot of energy.

The system in question is planet Earth. It has vast amounts of ice at its poles and around the equator on high mountains. Each year some of this melts and then is refrozen or replaced by more snow. For every cubic centimetre of water that is melted off the ice that then does not refreeze or get replaced by snowfall, 80 calories have been stored in the system. Each 1cc that fails to refreeze means 80cc of water is 1 degree further away from freezing. We are already seeing cubic kilometres of ice melting and not being replaced.

In other words, unless we reduce the amount of energy in the system, the ice will melt faster and faster until it is all gone, but the temperature will not start to climb appreciably until it is nearly all gone. It is called global warming not because the temperature is rising but because the amount of thermal energy being trapped in melt-water is rising.

Unless we take drastic action now, the Reverend Foster will find that prayer is the only thing left to him and he had better hope for divine intervention. To paraphrase Lord Rutherford: "everything is physics or it is stamp collecting".